The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years well architecture has become more sophisticated where appropriate in order to help enhance access to underground hydrocarbon reserves. For example, as opposed to wells of limited depth, it is not uncommon to find hydrocarbon wells exceeding 30,000 feet in depth. Furthermore, as opposed to remaining entirely vertical, today's hydrocarbon wells often include deviated or horizontal sections aimed at targeting particular underground reserves.
While such well depths and architecture may increase the likelihood of accessing underground hydrocarbons, other challenges are presented in terms of well management and the maximization of hydrocarbon recovery from such wells. For example, during the life of a well, a variety of well access applications may be performed within the well with a host of different tools or measurement devices. However, providing downhole access to wells of such challenging architecture may require more than simply dropping a wireline into the well with the applicable tool located at the end thereof. Thus, wellbore tubulars such as coiled tubing are frequently employed to provide access to wells of such challenging architecture.
Coiled tubing operations are particularly adept at providing access to highly deviated or tortuous wells where gravity alone fails to provide access to all regions of the wells. During a coiled tubing operation, a spool of pipe (i.e., a coiled tubing) with a downhole tool at the end thereof is slowly straightened and forcibly pushed into the well. This may be achieved by running coiled tubing from the spool and through a gooseneck guide arm and injector which are positioned over the well at the oilfield. In this manner, forces necessary to drive the coiled tubing through the deviated well may be employed, thereby delivering the tool to a desired downhole location.
With different portions of the well generally accessible via coiled tubing, stimulation of different well zones may be carried out in the form of perforating and fracturing applications. For example, a perforating gun may be suspended at the end of the coiled tubing and employed for forming perforations through the well wall and into the surrounding formation. Subsequent hydraulic fracturing applications may be undertaken in order to deliver proppant and further encourage hydrocarbon recovery from the formation via the perforations.
In some circumstances, a hydraulic jetting tool may be substituted for a more conventional perforating gun. A hydraulic jetting tool may comprise a solid body tool with jetting ports through sidewalls thereof and a ball seat positioned therebelow. Thus, once the tool is located at the target location for perforating, a ball may be pumped from surface and landed on the seat, thereby activating hydraulic jetting through the ports. Such a tool may be utilized where the nature of the surrounding formation dictates more effective perforating via a jetting tool.
Regardless of the particular perforating tool employed, the sequential nature of stimulation remains substantially the same. That is, coiled tubing is outfitted with a perforating tool which is delivered downhole to a target location to form perforations. The coiled tubing is then withdrawn from the well and the perforating tool swapped out for a hydraulic fracturing tool which is subsequently delivered to the same target location for follow-on fracing. However, even where the perforating tool is a hydraulic jetting tool, it may not subsequently be employed for the lower pressure hydraulic fracturing. That is to say, once the ball has landed, it is stably and irreversibly held in place while the tool is downhole, so as to ensure reliable jetting through the ports.
Unfortunately, the time it takes to run into and out of the well with the coiled tubing for the different stages of the stimulation can be quite costly, particularly when considering wells of greater depths or more challenging architectures. For example, it is not uncommon today to see wells of 10 to 20 different stimulated zones. Considering that in an offshore environment it may take on average about a week per zone to complete stimulation, the repeated trips into the well for tool change-outs may add up to several hundred thousand dollars of lost time. This is particularly true when considering the additional time required where clean-out between perforating and fracturing is undertaken or when considering separate well trips for zonal isolation in advance of stimulation.